Article: Nazerian, et al. “Integration of transthoracic focused cardiac ultrasound in the diagnostic algorithm for suspected acute aortic syndromes.” European Heart Journal 2019; 40:1952-1960.
Premise: The symptoms of abdominal aortic aneurysms (AAA) are often unspecific and the testing that can conclusively diagnose AAAs, CTA and TEE, often can’t be performed due to limited availability and cost or due to radiation/contrast exposure. One of these additional evaluations is Transthoracic focused cardiac ultrasound (FoCUS), particularly in combination with d-dimer. FoCUS has not been validated for its performance in assessing acute aortic syndromes by the European Society of Cardiology. Therefore, this article seeks to validate the algorithm of ADD-RS and FoCUS in the ED.
Study: This study was a secondary analysis of the ADvISED prospective multicenter diagnostic accuracy study, which took place at five tertiary centers in four countries from September 2014 to December 2016.
Included in this study were 839 patients with an average age of 62 who all underwent FoCUS for suspected AAA prior to advanced aortic imaging tests or surgery by cardiologist and non-cardiologist physicians with at least one year of experience in FoCUS. Each patient’s clinical probability of AAA was assessed using the ADD-RS and venous sampling for d-dimer were obtained in the ED and immediately sent to local lab. Subsequently conclusive imaging for AAAs was completed including one of the following: chest and abdomen contrast-enhanced multidetector CTA, TEE, and MRA. Patients with inconclusive diagnoses during their ED visit by CTA,TEE, MRA, or surgery were entered into a clinical follow-up case adjudication, dismissed from the ED with instructions to return if new or worsening symptoms arose. Two weeks after discharge, patients or family members underwent telephone interview using a structured questionnaire or underwent outpatient visit where they were asked about diagnosis of any aortic disease, ED visit, admission to the hospital, and death.
Primary Endpoints: 1) Determine if FoCUS can identify patients that will require CTA/TEE regardless of low probability for AAA. 2) Determine if Aortic Dissection Detection-Risk Score of low probability ( 1 or less ) coupled with negative direct or indirect FoCUS and negative d-dimer (<500) can rule out AAAs.
Results: There were a total of 146 patients (17.4%) determined to have AAAs. Direct FoCUS signs were detected in 84 patients (10%) and any FoCUS signs were detected in 307 patients (36.6%). FoCUS findings, except aortic regurgitation, were independent predictors of AAAs in addition to clinical variables and D-dimer. When integrating FoCUS with ADD-RS the diagnostic accuracy significantly increased. When direct FoCUS signs were detected in patients with a low pretest probability there was a posterior probability of 65%, whereas absence of direct FoCUS signs of AAA led to a posterior probability of 6%. Detection of any FoCUS signs in patients with a low pretest probability there was a posterior probability of 28%, whereas absence of direct FoCUS signs of AAA led to a posterior probability of 2%. When using ADD-RS of low probability and negative FoCUS to rule out AAAs, the sensitivity was 93.8% and the failure rate was 1.9%. Additionally, there was 100% sensitivity of rule out of AAAs in patients with low probability ADD-RS and negative direct or indirect FoCUS coupled with d-dimer. The specificity when using the direct FoCUS was 58.7% and indirect FoCUS was 48.4% when coupled with d-dimer in low probability ADD-RS patients.
Takeaways: This article ultimately highlights and validates that FoCUS is an efficient and accurate way to assess AAA in suspected patients. It is of particular utility in patients with low pretest probability ADD-RS scores when CTA and TEE are notoriously inconclusive. The results of FoCUS studies can then help reclassify patients accordingly and determine appropriate subsequent workup. Of note, Direct FoCUS signs for AAA are much more accurate than Indirect FoCUS signs and thus direct FoCUS should be used to avoid false positives and when upgrading probability. Despite the utility of FoCUS, they should not be used in isolation for assessment of AAA. However, FoCUS when coupled with d-dimer can safely be used to rule out AAA in low pretest probability patients when negative, which in turn suggests that CTA/TEE could be omitted without consequences in these patients.
Post by Mikhaila Smith-Wilkerson, MS4